JezK
Edit File: _musllinux.py
"""PEP 656 support. This module implements logic to detect if the currently running Python is linked against musl, and what musl version is used. """ import contextlib import functools import operator import os import re import struct import subprocess import sys from typing import IO, Iterator, NamedTuple, Optional, Tuple def _read_unpacked(f: IO[bytes], fmt: str) -> Tuple[int, ...]: return struct.unpack(fmt, f.read(struct.calcsize(fmt))) def _parse_ld_musl_from_elf(f: IO[bytes]) -> Optional[str]: """Detect musl libc location by parsing the Python executable. Based on: https://gist.github.com/lyssdod/f51579ae8d93c8657a5564aefc2ffbca ELF header: https://refspecs.linuxfoundation.org/elf/gabi4+/ch4.eheader.html """ f.seek(0) try: ident = _read_unpacked(f, "16B") except struct.error: return None if ident[:4] != tuple(b"\x7fELF"): # Invalid magic, not ELF. return None f.seek(struct.calcsize("HHI"), 1) # Skip file type, machine, and version. try: # e_fmt: Format for program header. # p_fmt: Format for section header. # p_idx: Indexes to find p_type, p_offset, and p_filesz. e_fmt, p_fmt, p_idx = { 1: ("IIIIHHH", "IIIIIIII", (0, 1, 4)), # 32-bit. 2: ("QQQIHHH", "IIQQQQQQ", (0, 2, 5)), # 64-bit. }[ident[4]] except KeyError: return None else: p_get = operator.itemgetter(*p_idx) # Find the interpreter section and return its content. try: _, e_phoff, _, _, _, e_phentsize, e_phnum = _read_unpacked(f, e_fmt) except struct.error: return None for i in range(e_phnum + 1): f.seek(e_phoff + e_phentsize * i) try: p_type, p_offset, p_filesz = p_get(_read_unpacked(f, p_fmt)) except struct.error: return None if p_type != 3: # Not PT_INTERP. continue f.seek(p_offset) interpreter = os.fsdecode(f.read(p_filesz)).strip("\0") if "musl" not in interpreter: return None return interpreter return None class _MuslVersion(NamedTuple): major: int minor: int def _parse_musl_version(output: str) -> Optional[_MuslVersion]: lines = [n for n in (n.strip() for n in output.splitlines()) if n] if len(lines) < 2 or lines[0][:4] != "musl": return None m = re.match(r"Version (\d+)\.(\d+)", lines[1]) if not m: return None return _MuslVersion(major=int(m.group(1)), minor=int(m.group(2))) @functools.lru_cache() def _get_musl_version(executable: str) -> Optional[_MuslVersion]: """Detect currently-running musl runtime version. This is done by checking the specified executable's dynamic linking information, and invoking the loader to parse its output for a version string. If the loader is musl, the output would be something like:: musl libc (x86_64) Version 1.2.2 Dynamic Program Loader """ with contextlib.ExitStack() as stack: try: f = stack.enter_context(open(executable, "rb")) except OSError: return None ld = _parse_ld_musl_from_elf(f) if not ld: return None proc = subprocess.run([ld], stderr=subprocess.PIPE, universal_newlines=True) return _parse_musl_version(proc.stderr) def platform_tags(arch: str) -> Iterator[str]: """Generate musllinux tags compatible to the current platform. :param arch: Should be the part of platform tag after the ``linux_`` prefix, e.g. ``x86_64``. The ``linux_`` prefix is assumed as a prerequisite for the current platform to be musllinux-compatible. :returns: An iterator of compatible musllinux tags. """ sys_musl = _get_musl_version(sys.executable) if sys_musl is None: # Python not dynamically linked against musl. return for minor in range(sys_musl.minor, -1, -1): yield f"musllinux_{sys_musl.major}_{minor}_{arch}" if __name__ == "__main__": # pragma: no cover import sysconfig plat = sysconfig.get_platform() assert plat.startswith("linux-"), "not linux" print("plat:", plat) print("musl:", _get_musl_version(sys.executable)) print("tags:", end=" ") for t in platform_tags(re.sub(r"[.-]", "_", plat.split("-", 1)[-1])): print(t, end="\n ")